Sensitivity to ethanol has been linked to the risk of developing alcoholism later in life in human studies. The research proposed here will identify DNA sequence polymorphisms in a model organism, Mus musculus, which influence the animal's sensitivity to ethanol. The Inbred Long Sleep (ILS) and Inbred Short Sleep (ISS) mouse strains have been selectively bred to have differential sensitivities to ethanol as measured by the duration of loss of righting reflex (LORR). Four Quantitative Trait Loci (QTL) have been mapped in these strains that have significant linkage scores to the sleep time phenotype. The genetic differences underlying these QTL could be either coding region changes that change the amino acid sequence of the resulting protein, or regulatory region changes that cause differential expression of the gene products. This proposal will determine whether gene regulation differences underlie any of the four QTL. Using CDNA microarrays expression of all known and hypothesized transcripts from the four QTL will be assayed. Baseline expression of these genes will be examined in ILS, ISS, and congenic lines. Suggestive expression differences found by the arrays will be confirmed by real-time RT-PCR. Genomic regions upstream of differentially expressed genes will be sequenced in ILS and ISS mice and polymorphisms between the strains will be identified. The sequence generated will then be surveyed for known or predicted regulatory regions using online databases and sequence prediction tools. Genes that have polymorphisms in their regulatory regions will then be assayed using in vitro transcription and cell culture transfection assays to link the sequence difference to the regulatory difference observed.